Polymers such as those prepared from methacrylate-butadiene-styrene ("MBS") monomers and polymers predominantly prepared from acrylic and methacrylic, referred to hereinafter as "(meth)acrylic," ester monomers are routinely employed as additives in polymeric matrices to provide products with improved impact properties. MBS polymers, however, are prone to thermal and oxidative degradation at elevated temperatures. (Meth)acrylic polymers used as impact modifiers for polymeric matrices, hereinafter termed acrylic impact modifiers ("AIMS") polymers, also are prone to thermal and oxidative degradation, although to a lesser degree than MBS polymers. This tendency of MBS and AIMS polymers to degrade at elevated temperatures inhibits the ability of these polymers to impart improved impact strength in polymer matrices such as polycarbonates and other engineering resins, as well as their blends which require relatively high processing temperatures.
MBS polymers that are employed as additives in polymeric matrices are routinely treated with stabilizers to protect them against thermal and oxidative degradation. Stabilizers, however, may cause the polymers to lose impact strength and develop colored impurities in the polymer matrix as a byproduct of their antioxidant action.
A need therefore exists for improved stabilizers for polymers such as MBS and AIMS and for improved polymeric products that employ the polymers which incorporate these improved stabilizers.